This invention relates to improvements in disposable diapers which utilize adhesive tape tabs for closure purposes. More particularly, this invention pertains to the inner facing of a disposable diaper which acts as a releasable protective surface for the adhesive tape tabs before use.
Disposable diapers with adhesive tape tabs for fastening purposes as well known and have been favorably accepted due to their beneficial features. The advantages of adhesively-treated tape tabs as replacements for pins are easily perceived, and have been put to good use on the known diapers. Though disposable diapers have been improved with the introduction of adhesive tape tab fasteners, a number of problems exist in those tape tab diapers which leave room for further improvement.
A number of the prior art diapers contain adhesive tape tabs which carry individual, removable release or cover sheets. These sheets protect the adhesive surface on the tape tabs during manufacture, storage and before use on the diaper. When the diaper is ready for use the release sheets are completely removed from the tape tab and from the diaper to expose the layer of adhesive beneath. The discardal of the small sheets of release paper poses the problem. Because the person preparing the diaper application, usually around an active infant, has that piece of release sheet in hand, it often becomes awkward to rid oneself of the release paper, hold the infant in position and fasten the tape properly and securely. Also, once the release sheet is discarded it must be done so properly so that the infant does not reach it and place it in his or her mouth, creating further problems.
Other prior art tape tab diapers do not have the discardal problem as above because these diapers contain a protective release sheet which remains fastened to the diaper. To expose the adhesive surface the tape tab is peeled from the release sheet, one surface of which is permanently attached to the diaper. Thus, no discardal of the release paper is required, thereby eliminating those problems associated therewith. However, since the release sheet stays permanently attached to the diaper, usually on the inside surface thereof, it may be an irritant to the wearer of the diaper if the diaper is not applied properly or if the diaper does not fit neatly. Besides this functional problem there are also economic problems inherent in these latter diapers. It adds more expense to not only include a protective paper over the adhesive tape tabs but to permanently fasten one surface of the protective paper to the diaper. The equipment for producing this arrangement to assure proper alignment and registration is also a factor in the economic evaluation of these diapers, especially when considering the high volume manufacture of these products.
Recent attempts have been made to overcome some of the problems associated with releasable protective sheets. In U.S. Pat. No. 3,885,566 there is disclosed an improved disposable diaper in which a water permeable facing sheet comprises areas of water-sensitive or water-soluble adhesive areas underlying the adhesive tape strips such that the adhesive portions of the strips rest releasably against the adhesively treated areas. By this technique no protective release sheets are required because the adhesive sections of the tape strips rest against the releasable sections of the facing material in storage and before use.
Concededly, the technique in U.S. Pat. No. 3,885,566 of eliminating the protective release sheets is one way of accomplishing such a result. However, the narrow scope of this technique, namely providing only water-sensitive or water-soluble adhesive areas, on the facing material, leaves room for use of adhesive agents which are not water-sensitive or water-soluble. Many known and standardly used release agents are water-insoluble and water-insensitive. In this respect, though, it is recognized that there have been attempts prior to the above-mentioned patent to treat portions of disposable diapers with water-insoluble release agents.
In U.S. Pat. No. 3,638,651 a disposable diaper is disclosed having water-insoluble release agents located on portions of the diaper inner facing to protect adhesive sections during storage in cartons and when folded. It is significant to note in the many different embodiments of this patent that the areas or portions of the diaper which contain the release agent are the corners or ends of the diaper. In no instance is it taught or suggested that the release agent be deposited in the portion of the diaper inner facing which covers the delicate body areas of the wearer and which of necessity, must be the most fluid pervious.
One explicable reason why only the ends or corners of this prior art patent are treated, and not the middle highly pervious section of the facing material, lies in the disadvantageous properties associated with the known release agents taught by the reference. While providing release properties to the associated sections of the facing upon which the adhesive tape tabs rest, these water-insoluble agents are known to act as water or fluid repellents while imparting stiffness and boardiness to the coated material. These latter characteristics are the antithesis of the desirable features expected of a disposable diaper; a water-repellent facing material will not allow the secreted fluid to penetrate through the facing material into the highly absorbent inner filling of the diaper; and a stiff, boardy surface in contact with the skin of the wearer readily causes irritation, discomfort and displeasure.
Although it appears logical and practical to treat the facing sheet only in the areas against which the adhesive tape tab will rest, as taught in the two abovementioned patents, this selective treating raises havoc with volumetric production causing economic deficiencies. Alignment and registration of the release areas coordinated with the tabs must be done precisely with the accompanying costs inherent in achieving such precision; furthermore, selective applicators for the release agent, and curing and drying equipment must be provided in line during the diaper production process, all detracting from the economic advantages to be expected from the final product.